Effect of the hydrogen flow rate on the structural and optical properties of hydrogenated amorphous silicon thin films prepared by plasma enhanced chemical vapor deposition

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Abstract

Hydrogenated amorphous silicon (a-Si:H) thin films were deposited from pure silane (SiH4) and hydrogen (H2) gas mixture by plasma enhanced chemical vapor deposition (PECVD) method at low temperature (400 °C) using high rf power (60 W). The structural and optical properties of these films are systematically investigated as a function of the flow rate of hydrogen (Fmath formula).The surface morphology is analyzed by atomic force microscopy (AFM). The characterization of these films with low angle X-ray diffraction revealed that the crystallite size in the films tends to decrease with increase in (Fmath formula). The Fourier transform infrared (FTIR) spectroscopic analysis showed that at low values of (Fmath formula), the hydrogen is predominantly incorporated in Si:H films in di-hydrogen (Si-H2) and (Si-H2)n complexes. However, with increasing (Fmath formula) the hydrogen bonding in Si:H films shifts from di-hydrogen (Si-H2) and (Si-H2)n complexes to the mono-hydrogen (Si-H) bonding configuration. Finally, for these optimized conditions, the deposition rate decreases with increasing Fmath formula (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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